The present application relates to manhole covers, and, more particularly, to a swing-out manhole cover.
Manhole covers are well-known and widely utilized. Generally, a manhole cover provides access for maintenance of infrastructure, for instance wiring or piping. Traditional manhole cover assemblies include a frame that is attached to the substructure housing infrastructure to be maintained. Examples of such substructure include the base for a road or sidewalk. The manhole cover may be locked for security or sealed leak-tight to prevent infiltration of external contaminants. The cover in a traditional manhole cover assembly is lifted up and away from the frame to gain access to the infrastructure. Because manhole covers are predominantly made of iron and can weigh often in excess of 100 pounds, the effort required to lift a manhole cover can be difficult and even injurious to the operator.
Spring-assisted manhole covers have been developed to lessen the effort required to open the cover. In a typical spring-assist manhole cover, the manhole cover is hinged to the frame such that the cover is rotated up and away from the frame. For example, with a horizontally oriented frame, the cover rotates upwardly in a vertical direction. In one particular pre-existing construction, torsion springs are installed on opposite sides of the hinge to assist in the lifting. One end of each of the torsion springs is secured in a hole in the cover, and the other end is fixed in a hole in the frame. This configuration does provide assistance in lifting the manhole cover, but may not be suitable for use in pressurized applications where holes in the cover and frame are prohibited. Also, this configuration is only suitable in locations where there is enough vertical clearance above the frame for the diameter of cover to rotate through. This system can be more expensive than other systems because of the cost associated with the torsion springs and their installation.
The above shortcomings can be amplified when the site for the manhole is elevated above ground level. An example of such an application is when an access portal is desired in above-ground pipelines. Lifting an elevated cover can be more difficult than lifting a ground-level cover because typically less lifting leverage can be obtained due to the relative height of the cover to the operator.